It is common to use a roofing washer with a fastener having a head and a shank, such as, for example, a roofing screw, so as to fasten a blanket of roofing insulation to a roofing deck. Typically, the roofing washer in its entirety is molded from a polymeric material, such as, for example, polypropylene. Alternately, the roofing washer is stamped from sheet metal, such as, for example, galvanized steel, whereupon the roofing washer may have a central insert molded from such a polymeric material.
As disclosed in Hasan U.S. Pat. Nos. 4,663,910, 4,712,959, and 4,757,661, it is known for the roofing washer to have a restraining formation, such as, for example, an annular lip, for restraining the head of a fastener, with which the roofing washer is used, so as to limit backward movement of the fastener relative to the roofing washer. Moreover, as disclosed in Hasan U.S. Pat. No. 4,757,661, it is known for the roofing washer to have axially disposed ribs arranged in a generally spiral configuration for coacting with such a lip.
Other roofing washers having various features for restraining fasteners against backward movement are disclosed in Sandquist U.S. Pat. No. 4,074,501, Dewey U.S. Pat. No. 4,545,270, and Reinwall U.S. Pat. No. 4,630,984.
This invention provides a roofing washer having improved features for restraining a fastener head against backward movement relative to the roofing washer.